This invention relates to a system for transmitting a pattern or picture. The system is well applicable to a facsimile transmission system.
It is usual in such a system to encode an original pattern by an encoder into an encoded signal by making use of correlation between successive picture information pieces with a view to compressing the signal bandwidth or the amount of the signal to be transmitted from a transmitter to a receiver. It has been intended that the original pattern encoded and transmitted to the receiver by reproduced into a faithful reproduction of the original pattern. It is, however, often desirable as in transmitting hand-printed letters to achieve a higher compression ratio even at the sacrifice of the faithfulness of the reproduced pattern.
It is also known to derive a thinned pattern representative of a skelton or a medial line of the original pattern in order to reduce the amount of the signal to be transmitted. Both boundary lines of the thinned pattern have been encoded into run length codes by an encoder of a conventional pattern transmission system. On the other hand, it is often objectionable that the thinned pattern is considerably unfaithfully representative of the original pattern. This is particularly the case when the original pattern is divided, on encoding, into picture elements with a low resolving power.